Method of and apparatus for grinding threaded members and the like



Aug. 30,

B. M. W. HANSON METHOD OF AND APPARATUS FOR GRINDING THREADED MEMBERSAND THE LIKE Filed March 27. 1925 8 Sheets-Sheet 1 bwgi 13mm Aug. 30,1927. 1,640,992

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UNITED STATES PATENT OFFICE.

mar I. w. HANSON, OI KAI-RD, CONNECTICUT; BULB A. HANSON AND CLAR-INC! 1. WHITNEY, EXECU'IOBS 01' 8A1!) BENGT K. W. HANSON, DECEASED.

mnon 0] m MAB-LTD! FOB GRINDING THREADED KEHBEBS AND m LIKE.

Application ma larch :1, 1025. mm I0. is).

This invention relates to the art of grinding, and has particularreference to an 1mproved method of, and a paratus for grindmg grooved orthreade members, such as 6 taps, thread cutting hobs, lead screws, orthe like, so as to give to the grooves or threads accuracy and precisionin all respects. The improvements of the present invention may beemployed for forming and finishing 10 threads, for instance, or forfinishing threads after the same have been roughed out, but they findpeculiar adaptability in finishing ooved or threaded members after thememfirs have been hardened.

Formerly, the practice followed in the manufacture of hardened groovedor threaded members, such as threaded gauges, taps, lead screws, and thelike, was to merely cut, by means of a metal tool, the threads asaccurately aspossible on a piece of metal before it was tempered, andthen harden the threaded member without taking any further steps toeliminate the inaccuracies and errors introduced into the thread by thehardening process. It may be here said that, from a practicalstandpoint, it is impossible to cut or true a thread on a hardened pieceof metal by the use of a metal tool, for no metal is known to existwhich will cut or shear a piece of metal of the hardness required, forinstance, in a tap.

More recently, I have to lowed the practice of truing the threads of atap or the like, after it has been hardened by means of a grinding wheelhaving a single cutting edge with a cross sectional shape correspondingto that of the groove of the thread to be trued, the wheel and tap beingmoved one longitudinally relative to the other, in accordance with thepitch of the thread, so that the wheel successively operated upon thethread convolutions from one end to the other of the threaded portion ofthe work. While this practice is of advantage, it is open to certainobjections, among which may be mentioned the length of time required totrue the thread on the work, it being necessary to repeatedly move thegrinding wheel or work axially of the work the full length of thethreaded portion thereon, and considerable time is also consumed inrepeatedly truing the single edge of the grinding wheel, which edge hasto bear the entire burden or brunt of grinding the thread from end toend. Furthermore, errors, during the grinding operations, are very aptto occur ue to the relatively rapid wearing down of the wheel and thenecessity of more or less frequently displacing the grinding wheelrelative to the work for the purpose of .resurfacing or shaping thewheel.

The aim of the present invention is to provide an improved method of,and apparatus for, grinding grooved or threaded members, particularlyafter they have been hardened, wherein the above and other objectionsand disadvantages incident to the practices heretofore followed areeliminated and, more particularly, to provide certain improvements inthe art of grinding, by means of.whi'ch the grooves or threads may bequickly and economically ground with extreme accuracy in all particularsso that a superior product may be more economically produced.

Broadly speakin my invention contemplates an improve method, and aparatus or carrying the same into effect, w herein a plurality ofconvolutions, for instance, of the thread to be operated upon, aresimultaneously ground by a grinding wheel having a plurality ofconcentric cutting edges or ribs. By proceeding in accordance with thepresent invention,-since, instead of a single grinding edge doing allthe work, a number of grinding serrations are simultaneouslyefi'ective,the speed at which the grinding operations are performed isvery greatly increased, and the wear upon the serrations is materiallydecreased so that the time consumed in maintaining the grinding wheel incondition for accurate grinding is considerably reduced. Furthermore,the likelihood of errors in the work, due to the rapid wearing down of agrinding wheel with a single cutting edge, and the necessity offrequently truing that edge, is substantially eliminated or, at least,reduced to a minimum. This all means that the rate of production and thecapacity of the machine are very high, while, at the same time, theoperations are carried out with accuracy and precision so that thepieces of work are very superior and may be economically manufactured.

A. generic object of the present invention is to prevent the work frombecoming overheated and turning blue and having its temper drawn owingto the heat generated by the abrasive action of the plurality ofserrations. To this end, the serrations of the grinding wheel are soarranged and constructed that a cooling fluid may be passed, during theentire grinding operation, throu h spaces provided between the grindingw eel and each of the convolutions of the thread operated upon. Afurther advantage of the. arrangement of the serrations on the wheel isthat the heat of the abrasive action on each convolution or rib on thework, since each convolution at any one instance is operated upon on oneside face only, is relatively less than would be the case if both sidefaces of the convolutions were simultaneously opera-ted upon by theserrations. The arrangement of the serrations on the grinding wheel, inaddition to providing spaces through which a fluid may pass so as tomaintain the work relatively cool duringthe grinding operation, is alsoof advantage in that the serrations may be accurately trued, there beingample room between the serrations to accommodate truing mechanism ashereinafter described more in detail.

A further aim of the' present invention is to provide a machine orapparatus of the character described with means for shaping or truingthe serrations of the grindin wheel, the arrangement being characterizedby various features of novelty and advantage, and, particularly, by theaccuracy and facility with which the serrations may be shaped and trued.

In accordance with one species of the in vention, and to which speciescertain of the appended claims are particularly directed, the cuttingedges, serrations, or ribs of the grinding -wheel are so arranged andconstructed that they will successively grind increments from thesuccessive convolutions or grooves of the work; that is to say, theserrations will grind the work down to the proper form in stages orsteps, each rib or serration performing that portion of the dutyassigned to it. It is to be understood, however, that my invention,broady considered, and certain of the appended claims, are not limitedto this species of the invention.

Other objects will be in part'obvious and in part pointed out more indetail hereinafter.

The principles of the invention may be embodied or employed in machinesof appropriate construction or design. In the accompanying drawings Ihave shown two forms of a paratus, either of which may be employed orcarrying out the generic features of the invention, but it is to beunderstood that these showings are merely by way of illustration.

This is in part a continuation of my application Serial No. 754,745,filed December 9, 1924.

Figures 1 to 3 inclusive, illustrate, more or less diagrammatically, amachine and process disclosed in my application Serial No. 640,351,filed May 21, 1923; said application 754,745 having been filed as adivision, in part, of said application 640,351.

Figures 4 to 10, inclusive, illustrate a machine which, together withthe method involved in it's use, in so far as they constitute adifferent species ofthe'generic invention, is made the subject-matter ofmy co-pendin application, Serial No. 691,643, filed Feb= ruary 9, 1924.I Figure 1 is a diagrammatic view showing, in top plan, one form ofapparatus which may e employed for carrying out the invention;

Fig. 2 is a diagrammatic view similar to Fig. l and showing a difierentform of wheel and truing device, a portion of the wheel beingexaggerated;

Fig. 3 is an enlarged diagrammatic View showing the manner in which theserrations of the grinding wheel, disclosed in Fig. 1, successively outsmall incrementsfrom the thread;

Fig. 3* is a view similar to Fig. 3 and shows the manner in which athread or groove is ground when the grinding wheel, illustrated in Fig.2, is employed;

Fig. 3 is a similar view showing the manner in which a VVhitworth threadis ground;

Fig. 4 .is a front view of another form which the machinemay take;

Fig. 5 is a left hand end View of the machine of Fig. 4;

Fig. 6 is a view showing more or less diagrammatically, the manner inwhich the grinding wheel, employed in the machines of Figs. 4 and 5,operates upon the work;

Fig. 7 is a vertical sectional view taken substantially on line 77 ofFig. 4, the truing device being omitted;

ig. 8 is a plan view of the left hand side of the machine of Figs. 4 and5, with parts in section and other parts removed for purposes ofclearness;

Fig. '9 is a detail view showing, in horizontal section, the cam forreciprocating the work'holder and the cam for. controlling the feedingmovement of the work relativelyto the wheel and the withdrawal movementof the work upon its return stroke, this view being taken substantiallyon line 99 of Fig. 7

Fig. 10 is a diagrammatic view showing the relation between these cams;

Fig. 11 is a view similar to Fig. 6 but showthread;

Fig. 12 is a to plan view of the truin device which may employed ineither the machines illustrated;

Fig. 12* is a detail view of parts of the indexing means of the truingdevice;

Fig. 13 is a sectional view through the truing device and shows the samecarried by the rockin bed of the machine illustrated in Figs. 4 an 5;

F'g. 14 is a detail view taken substantially on the line 1414 of Fig.12;

Fig. 15 is a diagrammatic view showing the relative angular positions ofthe inding wheel and work when the latter as a thread of large lead tobe ound;

Fig. 16 is an end view 0 the arrangement shown in Fig. 15 andadditionally indicates the osition of the device for truing the whee andFig. 17 is a detail view showing an arrangement which permits theangular adjustment of the grinding wheel.

Referring to the drawings, and particularly to that embodiment shown inFigs. 1 to 3", inclusive, is a base upon which is slidabl mounted thegrinding device here shown as cing in the form of a grinding wheel 11'having a plurality of serrations, as hereinafter described. 12 is acarriage on which the work is supported, in the present instance thework supportin means being in the form of head and tail stocks 13 and14, respectively the head stock being provided with a sphned spindle 15.In the selected illustrative disclosure, during the rinding operationthe wheel is rotated rapidly but has no movement in the direction of itsaxis, and the work, indicated by the letter W, is slowly rotated by thedriven spindle 15 and is moved axially, as by means of the lead screw16, the relative motions of the work being so proportioned that theserrations provided on the periphery of the grinding wheel will form orfinish the thread or threads of the work to the desired lead. The workspindle 15 and the lead screw 16 may be driven one from the other, asthrou h suitable change gears 24. It is, of course, 0 vious that thearrangement may be such that either the work or the grinding Wheel, orboth, may be moved to effect the desired pitch of thread on the work.The grinding wheel is mounted on a shaft 17 journalled, as at 18, on aslide 19, which may be moved towards and away from the work in anysuitable manner, as by means of a screw 20 having a hand wheel 21. Ifdesired, the screw 20 may be provided with a micrometer 22. by means ofwhich fine adjustment in positioning of the grinding wheel may be had. Apulley 23 may be provided on the shaft 17 to rotate the grinding wheel.A nozzle or spout is rovided to direct a flow of a suitable coolingfluid onto the work.

The grin ing device 11 is in the formpf a cylindrical member formed ofabrasrve material such as carborundum, and has on its periphery aplurality of serrations or cutting edges 25, 25", etc. By preference,each of these serrations is in the form of a separate continuousconcentric ring or rib to the plane of which the axis of the wheel isperpendicular. One of the generic features of the present inventionresides in so arrang-' ing or shaping these serrations or cutting edgesof the grinding device (whether or not said edges are ste ped orarranged for increment grinding) t at a cooling fluid, during thegrinding operation, may pass between the grinding wheel and each ri orconvolution of the work operated upon so as to minimize the heatingeffect of the abrasive action on the work and thereby prevent the latterfrom having its temper drawn. This object may be accomplished byvariously arranging or shaping the serrations, as, for example, bymaking the grooves 9 in the grimling wheel relatively deeper than theactual grinding surfaces of the serrations. The side faces of theserrations may be trued for a distance less than their depths. Bypreference, the serrations in the grinding wheel may be so arranged thatat any given time each of the convolutions of the work is operated uponon one face only; for instance, the serrations or cutting edges of thegrinding wheel may be spaced apart a distance further than that betweenadjacent convolutions so that the serrations will grind non-adjacentconvolutions of the thread groove. It is to be understood that thepresent invention is susceptible of use in grinding grooves and threadsof various forms on pieces of work of different kinds, andthe machinesillustrated in the drawings may be employed for grinding multi-threadsas well as single threads. In certain of the figures, the serrations ofthe grinding wheels are shown as being spaced apart so that they occurat every other convolution on the thread of the work, it being obvious,however, that they may be otherwise s aced depending upon the characterof tie work. B preference, the serrations or cutting edges of thegrinding wheel are spaced apart equal to a multiple of the distancebetween the successive convolutions of the screw operated upon. Where athread of very fine pitch is to be gound it may be found to be ofadvantage to space the serrations three or four times the distancebetwen the adjacent convolutions of the thread on the screw. Asexplained hereinafter more in detail in connection with the descriptionof the truing device, the arrangement of the serrations on the rindingwheel in addition to providing cooling fluid passages therein permitsready and accurate truing of the grinding faces of the serrations, therebeing ample room between the serrations to insert the diamond points.

In accordance with that species of the invention shown in Figs. 1 to 3",inclusive, the grinding wheel is arranged so that its serrations willsuccessively grind increments from the successive grooves orconvolutions of the work. To this end, the grinding device may haveserrations or cutting edges of varying or difierent sizes or shapes orboth, so that, as the rinding wheel is passed longitudinally of thework, each cutting edge or serration will perform but a portion of thegrinding operation, the first cutting edge rinding away a small portionor portions rom the sides or (and) root of the thread grooves, as thecase may be the second serration taking off a little more, either fromthe same part, face or portion of the thread convolutions, and on whicha previous serration operated, or on a different face or portionthereof, and so on until the thread groove is of a proper size and shapein cross section.

In the illustrated disclosures of. Figs. 1 to 3", inclusive, I haveshown the grinding wheel serrations as being of successively increasingdiameter or hei ht, and'at equal distances from the axis 0 the wheel, asbeing of successively increasin width, so that the successive serrationswil progressively grind small increments from the sides and root of thegroove of the threaded member, but it is to be understood that thisshowing is by way of exemplification only and. if desired, theconstruction may be such that the successive serrations will grinddifferent portions of each thread convolution or groove, as, forexample, one serration may grind one face or portion of the threadgroove and the next one will grind the other ace or the root thereof,and so on. If desired, the serrations may be so arranged that they willprogressively grind successive increments from the root of the threadgroove or from both the sides and the bottom or root of the groove orportions thereof.

Referring more specificall to the grinding wheel shown in Fig. 1, t eserrations of the wheel are formed to grind V grooves or threads on thepiece of work or tap. It will be seen that the successive serrations areof progressively increasing size in, at least, one dimension, in thepresent instance, the serrations being all of substantially the sameshape and of progressively increasing diameter so that they willprogressively grind small portions from the sides and root of thegroove. The serration 25 is slightly higher, i. e., of greater diameter,than the preceding one 25, the serration 25" slightly higher than theone 25, and so on, until the final serration is reached (in the presentinstance, the serration 25) which, in cross section, preferablycorresponds exactly to the cross section which it is desired to give tothe thread groove. It will be noted that these serrations are ofprogressively increasin width at like distances from the axis of t ewheel. When the arrangement shown in Fig. 1 is employed, the work W ismounted between the work centers of the head and tail stocks, thegrinding wheel is properly positioned relative to the work and then thepower is thrown on whereupon the work will be moved axially by the leadscrew 16 while the work is rotatively driven at the proper rate of speedthrough the gears 24. The serration 25 will rind a small V-shapedincrement 25' (see Fig. 3); the next serration 25 will grind anadditional increment 25, and so on until finally the serration 25 willtake an increment 25 thereby finishing the thread to the exact sha e andsize.

he grinding wheel shown in Fig. 2, and desi nated by the character 11,is generally simi ar to the grindin wheel shown in Fig. 1 with theexception t at the serrations are truncated. These serrations,designated by the numerals 26, 26, 26 and 26, are of progressivelyincreasing height and, preferabl their truncated ed es are of substantialy the same width. he serrations are of similar shape and are shown asbeing spaced apart so as to operate at any one moment on every otherconvolution of the thread roove. When this wheel is em ployed orgrinding a grooved or threaded member, the serrations will grindsuccessive increments, respectively designated '0 the characters 26,26", 26" and 26, as s own in Fig. 3.

Fig. 3 diagrammatically illustrates the successive increments which agrinding wheel would take from a piece of work, the grinding wheelhaving its serrations so formed as to grind a Whitworth thread. Theconstruction of the grinding wheel and its mode of use would be similarto those described in connection with the grinding wheels illustrated inFigs. 1 and 2.

It will thus be clear, from the foregoing, that it is possible toaccurately grind the thread of the work by relatively passing thegrinding wheel but once axially of the work, and since a plurality ofedges or ribs are operating simultaneously, the time required to finallyrind the threaded 0r rooved member an take out all the imperfections andinaccuracies therein, due to hardening or other causes, will bematerially reduced, so that the work can be economically ground.

Reference will now be had to the machine shown in Figs. 4 to 10,inclusive. In this instance, the machine is provided with a grindinwheel having serrations similar to those 0 the'wheel of the precedingembodiment, except that the serrations are all of rinding wheel and worktoward each other 1S intermittently eflectcd so that the grinding wheelwill take successive cuts. The serrations of the grinding wheel are soarranged or constructed that a cooling fluid ma be passed between thegrinding wheel an each of the thread convolutions operated upon, as inthe precedin embodiment.

Referring more s eci cally to Figs. 4 to 10, a denotes the xed bed orbase; 6, a rocking bed thereon; a, a work holder mounted forreciprocation on the rocking bed substantially in parallelism with theaxis about which said bed is rocked, and having head and tail stocks dand 0, respectivel f, a ear box mounted on the rocking ed; an 9, agrinding wheel mounted in a suitable bearing box It carried by a slide2', the latter being mounted on the base a for adjustment at rightangles to the axis of the work.

The rocking bed b is L-shaped in plan and is mounted for rockingmovement on suitable knife edges (see Figs. 4 and 5) positioned at theforward corners of the base a. The work holder comprises, generally, amain slide 53 mounted on ways 54 on the iongitudinally extending portionof the rocking bed b a su plementa'l slide 55 mounted on the main sli eand adapted to be adjusted thereon by a screw 56, and the head and tailstocks d and e mounted on a supplemental slide 55. The tail stock may beadjusted as desired. The grinding wheel g is generally cylindrical andhas a plurality 0 cutting *dges or ribs 57 (see Fig. 6) all of which are)f the same size and shape. Each serration conforms exactly to the shapeof the groove of the thread operated upon. In the present instance, theserrations or cutting edges of the wheel are spaced apart so that theywill grind non-adjacent convolutions of the thread grooves, whereby theheating effect, due to the abrasive action of the wheel on the work, isminimized, and suflicient space is provided between the serrations toermit' of the flow of a suitable cooling fluid t ereto. The grooves 58between the serrations of the wheel are relatively deeper than theactive grinding faces of the serrations so as to provide the coolingfluid passages. In the present instance, wherein it is assumed that thework has a single thread, the serrations or cutting edges on the wheelare shown as spaced apart at a distance twice the pitch of the threadand, in this case, it is necessary to rotate the work about two completerevolutions during each operative stroke of the work in order that thegrindin wheel will operate upon the thread throu out its entire length.It is, of course, un erstood that the serrations of the grinding wheelmay be spaced apart other than at twice the distance of the pitch of thethread being ground. The grinding wheel maybe rotated in any suitablemanner, as by means of a belt, passing about a pulle (not shown) securedto the grinding whee spindle. The slide 71 on which the grinding wheelis mounted may be adjusted radially of the work in any suitable manner,as by means of a hand screw 59 shown in Fig. 5.

Pivoted, as at 62, in a: bracket 63 fixed to the rearwardly extendingarm or leg 64 of the rocking bed I), is a rocking beam 65 through whichcertain mechanism or instruinentalities operate to rock the bed andthereby move the work towards and away from the grinding wheel (seeFigs. 7 and 8). One of said mechanisms is that for swin 'ng the rockingbed with a succession of small movements so as to feed the work to thewheel. This feeding mechanism includes a nut 66 mounted for slidingmovement in a bore within the bracket 63. To the lower end of the 'nutis keyed a Worm wheel 67 which is in mesh with a worm 68. In threadedengagement with the nut 66 and keyed against rotation relative to thebracket 63, as at 69, is a screw 70 having a hearing at its lower end ona block 71 rising from the base 11. Supported in the upper end of thenut 66 is a pin 73 on which the short end of the rocking beam or lever65 rests. The worm 68 is carried by a shaft 75 which, as shown clearlyin Fig. 7, extends through the rocking -bed to the front of the machine.This shaft may be manually rotated by hand wheel 76 to preliminarilyadjust the work radially of the wheel. This shaft is intermittentlyrotated through mechanism, including the cam R, hereinafter more fullydescribed in detail, for the purpose of swinging the rocking bed aslight distance toward the grinding wheel each time a new cut is to betaken. It is to be understood that, when the shaft 75 is rotated, thenut 66 is turned so that it will move up or down, as the case may be, onthe screw 70 and thereby vary the distance between the u per end of thepin 73 and the lower end of the screw 70.

Another mechanism which cooperates with the rocking beam in order tomove the work relatively to the wheel is in the form of a cam 78. Thiscam is intermittently rotated so as to lift the work away from thegrinding wheel on the return stroke of the work holder and to againbring the work into onerative position when a new cut is to e taken. Asshown most clearly in Fig. 7, it engages the underside of the long armof the rocking beam 65. The cam is secured to the ing bed includes ainner end of a shaft 7 9 journailed in the gear box and this shaft isintermittently rota'te 180 through suitable mechanism which includes anesca ement ratchet clutch controlled by the cam associated with the camS, as hereinafter described more in detail.

The third mechanism for rocking the rockattern cam 82 which may be usedwhen it is desired to cut an irregular circumferential contour on thework as, for instance, when it is desired to relieve the teeth of a tap.In the present illustrative disclosure, this cam (see Fig. 7) has fourlobes or rises corresponding to the four lands of a four-fluted tap. Itis fixed to the end of a shaft 83 which is geared up to the work s indle84 so as to rotate in synchronism t erewith.

The eccentric cam 78 which, for convenience, will be termed a liftingcam, the pattern cam 82, and the work spindle 84, are driven throu h thefollowing arrangement: Journalletf in the ear box I is a xed a pu ley 86main shaft 85 to which is driven by means of a belt (not shown) assingthereabout. On the inner end 0 the shaft 85 is a gear 87 meshing with asmall gear 88 fixed to a stub shaft 89 which carries a gear 90 whichdrives a clutch gear 91 adapted to be fixed by a clutch 92 to the shaft83. On the outer end of this latter shaft is a gear 94 meshi with a ear95 fixed to a s eeve 96 journa led in a caring 97. Extending through thesleeve 96 for sliding movement, but s lined thereto so as to rotatetherewith, is t e work spindle 84. The pattern cam 82 which, as stated,is fixed to the shaft 88, and the work spindle 84 are each continuousldriven in a single direction. To stop t e machine, the handle 98 may bethrown into off position. This handle is fixed on a. pin 99 whichcarries, within the gear box, a shipper lever 100 having a roller engaing in a groove of a sleeve 101 splined on t e shaft 83 and associatedwith the clutch 92. This clutch is shown diagrammatically, as it may beof any suitable construction, it being sufficient to say that when thesleeve 101 is moved in one direction the clutch is thrown out, and whenmoved in the other direction it is thrown in.

The shaft 79, on which the lifting cam 78 is fixed, is intermittentlyrotated throu h an escapement clutch shown in plan in 1 8, and inelevation and by dotted lines in l ig. 5. Normally loose on the shaft 79is a unit including a sleeve 104, a gear 105, and a ratchet wheel 106.The gear 105, together with the sleeve 104 and the ratchet wheel 106, iscontinuously driven by a ear 107 fixed on the main shaft 85. Fixe to theshaft 79 is a disk 108 to one face of which is 'pivoted a pawl 109 whichis normally urged into with the teeth of the ratchet wheel 106 by aspring pressed plunger 110. intermittent enga ement of the pawl with theratchet wheel 15 controlled by an escapement mechanism which includes apair of pivoted levers 111, the inner ends of which are diametricallydisposed relative to the ratchet wheel 106. The outer ends of theseescapement levers are, by means of spring pressed plungers 112,maintained against opposed abutments 113 upon a vertically movable rod114 connected at its lower end to a lever 115 fixed on a shaft 116 whichextends through the rocking bed to the front of the machine. This shaft116 is controlled by means of the cam R which also automaticallycontrols the operation of the variable connection b means of which 'thework is fed towards t e grinding wheel each time a new cut is to betaken. When this cam R rocks or rotates the shaft 116 in one direction,the rod 114 is lowered, whereupon the upper escapement lever 111 ismoved in a direction to releasethe pawl 109 and the lower lever is movedinto the path of movement of this pawl. This pawl, thus released, willengage the continuously rotatin ratchet wheel 106 so that the shaft 79an the ratchet wheel will rotate in unison. This rotary movement of theshaft 79 is limited to 180 because when the pawl has rotated to thatextent it is disengaged from the ratchet wheel by the lower lever 111.When the shaft is thus rotated 180, it may be assumed that the cam 78fixed thereto raises the long end of the lever of the rocking beam 65,which means that the rocking bed will be swung in a direction to movethe work away from the grinding wheel. When the shaft 116 is rotated inthe other direction, the lower escapement lever 111 is moved out of engement with the pawl 109, whereupon the s aft 79 will be rotated another180, and, during this time, the cam 78 will be rotated to the positionshown in Fig. 7, thus permitting the long end of the rocking beam tocome down, which means that the rocking bed is moved in a direction tobring the work into operative relation to the grinding wheel.

On the forward end of the shaft 75, which is connected to the feedmechanism including the nut 66, is a ratchet wheel 120 and a pivotedlever 121 (see Figs. 4 and 8). One end of this lever carries a pivotedpawl 122 cooperating with the ratchet wheel 120. The other end of thelever 121 is connected by a link 123 to one arm of a bell crank 124fixed to the forward end of the shaft 116. The other arm of the crank isconnected by a link 125 to a T-lever 126. One arm of this lever 126 isconnected by a link 127 to a shipper lever 128 which carries a roller129 cooperating with the cam B. When the T-lever 126 is rocked in onedirection, in the present instance, clockwise, the lever 121 is rotatedin a clockwise direction so that the pawl 122 will rotate the ratchetwheel 120, together with the shaft on which it is fixe in a directionwhich will result in the nut 66 of the feed mechanism moving down on thescrew 70, whereu on the rocking bed will swing downwar ly and rearwardlyto a slight extent to feed the work relative to the grinding wheel. Whenthe T-lever 126 is rocked in counterclockwise direction, the pawl 122 ismoved counterclockwise, during which time it will ride over the teeth ofthe ratchet wheel without im parting rotation thereto.

The cam R is fixed to a shaft 136 which also carries the cam S for movinthe work holder on its operative and moperative strokes. This shaft isdriven from the work spindle in a single direction in any suitablemanner, as, for instance, through the train of gears 137, 137", etc. Thefirst gear 137 of the train is fixed to the sleeve 96, shown mostclearly in Figs. 5 and 8, and the last gear 137 is fixed to the outerend of the shaft 136. The gear 137 is a change gear carried b a rockerarm 138. The cam S has a circum erential groove in which engages aroller or follower 141 journalled on a pin 142 driven into a lug 143extending from a flanged bushing 144 fixed in a bore 145 in the lefthand end of the main slide 53 of the work holder. The parts 141, 142 and143 are shown in dotted lines in Fig. 9 since, in the other figures,they are above the plane on which Fig. 9 is taken. The inner end of theshaft 136 has a bearing in this bushing 144 so that the shaft is heldagainst fiexure and vibration. The cam groove has a pitch portion 140and a return portion 140". The cam surface 140 of the pitch portion, andagainst which surface the follower 141 engages while the cam is movingthe work holder on its operative stroke, is so inclined as to move thework axially at a rate corresponding to the pitch of the threadbeingground. This cam surface extends more than half way round the cam, itbeing of such length as to move the work holder axially of the workduring the time required to bring the work into engagement with thewheel. to grind the work, and then move the work away from the wheel,and during this time the work spindle is given more than one completerevolution. In the present illustrative disclosure. since it has beenassumed that a piece of work having a single thread is operated upon andthe grinding wheel has its serrations spaced apart at a distance twicethe pitch of the thread, the pitch portion of the cam is of such lengththat 1t moves the work holder on its operative stroke while the work ismaking four complete revolutions. During the first revolution of thework, the latter is being brought into engagement with the wheel; duringthe second and third revolutions the grinding wheel is operating uponthe work, and during the fourth revolution the work is being moved awayfrom the 7 it is immediately picked up by the other. so

that there is substantially no lost motion. The cam S is keyed to theshaft 136 and it is secured against longitudinal movement, and in anydesired position of adjustment on the shaft 136, by a clamping screw 151passing through spring fingers or portions 152 of the cam.

The cam R (see Figs. 8, 9 and 10) includes a sleeve 155 and dogs 157,158, adjustably secured thereto. In the present illustrative disclosure,the sleeve has a circumferential T-groove 159 which receives squareflanged nuts 160. The dogs are secured to these nuts by bolts 161. Thedog 157 has a cam surface 157 which. while the cam S is just completingthe operative stroke of the work holder, engages the roller 129 andthrows the shipper lever 128 in a direction to so actuate the escapementclutch mechanism that the lifting cam is turned from the position shownin Fig. 7 so as to swing the rocking bed upwardly and forwardly and thuswithdraw the work from the grinding wheel. Also, when the shipper lever128 is thus turned. the pawl 122 is moved in that direction(counterclock wise) in which it will ride over the teeth of the ratchetwheel 120 without turning the feed shaft 75. The dog 158 has a camsurface 158' which, while the cam S is beginning the operative stroke ofthe work holder, throws the level 128 in a direction to cause the pawl122 to rotate the feed shaft 75 and also to cause actuation of theescapement clutch mechanism, whereupon the lifting cam will be rotated180 to the position shown in Fig. 7. Thus, when the cam surface 158 isactuating the lever 128. the feed mechanism is actuated to feed the workslightly towards the wheel. and the lifting cam is turned to swing therocking bed downwardly and rearwardly to bring the work into operativeposition relative to the wheel. The cam R is splined to the shaft 136 bya key 163 extending into a groove 150 in the shaft 136. The cam R isclamped against longitudinal movement on the shaft 136 between a bushing164 and a nut 165, the latter being locked in place by a clamping screw166. The bushing 164, through carrries the change gear 137".

The operation of the machine shown in Figs. 4 to 10, inclusive, isbriefly as follows: A cam S, the cam surfaces of which will depend uponthe pitch of the thread to be ground, the number of threads on the workand the number of serrations on the grinding wheel, is selected andsecured on a shaft 136; the proper change gear 137 is secured to therocker arm 138, and the dogs 157 and 158 are properly adjusted. Assumingthat the machine has been thrown intooperation and the work holder iscompleting its operative stroke, the cam surface 157 will engage theroller on the shipper lever 128 and, through the connections described,will move the pawl 122 in that direction in which it will ride over theteeth of the ratchet wheel 120. Also, when this lever is thus thrown,the upper escapement lever 111 will be released from the pawl 109whereupon the lifting cam 78 will be rotated 180 from the position shownin Fig. 7, and when this cam is so rotated, it will swin the rocking bedupwardly and forward y so as to withdraw the work from the grindinwheel. The cam surface 140 of the cam will now come into play to movethe work on its return or inoperative stroke. After the work has beenmoved on its inoperative stroke, it is again started forward by the camsurface 140 on its operative stroke, at which time the cam surface 158"will come into play and throw the lever 128 in a direction to cause thepawl 122 to rotate the ratchet wheel 120, which, acting through the feedmechanism, will swing the rocking bed slightly downwardly and rearwardlyso as to feed the work a slight distance towards the wheel. About thistime, the escapement ratchet clutch mechanism is a ain operated so thatthe lifting cam 78 wil rotate 180 to the position shown in Fig. 7, thuspermitting the rocking bed to swing downwardly and rearwardly and bringthe work into operative relation to the grindin wheel. WVhile the workis being brought into engagement with the grinding wheel, as justdescribed, the work is making one revolution and it is being moved bythe cam S in accordance with the pitch on the work. The cam Swillcontinuesto move the work holder in accordance with the pitch of thethread while the work is making two more revolutions, and, during thistime, the grindin wheel is operating on the work. The cam continues tomove the work in accordance with the pitch of the thread thereon duringthe time that the work is moved out of enassesses gagement with thewheel, and then the return portion of the cam S, while the work ismaking another revolution, will return the work to its original point.This sequence of operations is re eated until the threaded member hasbeen rought down to desired size. During the entire grinding operation,a cooling fluid is passed between each of the convolutions of the threadand the grinding wheel; that is, the fluid flows through the passages orgrooves 58 in the wheel. The coolin fluid may be applied through anozzle 1 0 positioned above the line of contact between the grindingwheel and work.

Referring to Fig. 11, there is shown a grinding wheel 9' having aplurality of serrations 57' operating upon a member or screw having anAcme-or truncated thread. In this instance, the grinding serrations ofthe wheel are spaced apart a distance equal to that between adjacentconvolutions of the thread, so that there is a grinding serrationoperating upon each convolution. This arrangement may be adopted wherethe three is similar to an Acme and is of relatively large pitch, inwhich instance there is sufiicient metal in the thread to carry awa partof the heat nerated during the grin mg operation. t will be seen fromthis figure, that the grooves 58' between the serrations of the grindingwheel are relatively deeper than the active grinding side faces of theserrations, so that there is a space left between the grinding wheel andthe to of each convolution of the thread throu which a cooling fluid maypass during t e grinding operation. The 'nding wheel, shown in Fig. 11,ma be substituted for the one in 'the machine illustrated in Figs. 4 to16, in which case a cam, similar to the cam S, will be selected buthaving its cam surfaces so arranged that it will move the work on itsoperative stroke a distance equal to the pitch of the thread operatedupon, during which time the work will make one complete revolution. Thedogs 157 and 158 will be adjusted so that they will function in properrelation to the cam S.

It will be obvious from the foregoing descriptions that in each of theembodiments illustrated, since, during the grinding operation on thework, a plurality of serrations or cutting edges are simultaneouslyeffective, and these serrations each perform but a relatively small partin grinding away excess metal from the work to bring the thread to thedesired size and shape, grinding of the work may be very quickly carriedout with precision, and the grinding wheel will not weanout as rapidlyas would be the case where a single cutting serration is provided sothat repeated truing of the wheel is not required, all of which meansthat threaded members, perfect in all respects, may be pro- .duced in ashorter space of time with less labor and at a materially reduced cost.As hereinafter explained more in detail, when the wheels do need truing,they may be reshaped very accurately and quickl It will be further seenthat in eac embodiment illustrated, since, during the entire indingoperations a cooling fluid is passed tween the wheel and each of theT1118 or thread convolutions on the work, the heat enerated by theabrasive action is prevented 510m heating the work to such an extent asto injure the same as, for example, by drawing its temper. As stated,the flow of cooling fluid may be provided for by making the oovesbetween the serrations of the rinding wheel substantially deeper than te active grinding faces of the serrations, and, by preference,particularly where the pitch of the thread to be ground is relativelysmall, the serrations of the inding wheel are spaced apart at a multlpleof the distance between adjacent convolutions of the thread or threads.With the arrangements described, the extent of relative movement betweenthe grindin wheel and work, axially of the latter t rough a distanceequal to that between corresponding points of corresponding grindingfaces of adjacent ponvolutions, is greater than the projections onto theaxis of the wheel, of the active grinding surfaces of the serrationsbetween these oints. This will be very readil understoo from Figs. 2, 6and 11. The distance between two corresponding points of adjacentserrations of the grinding wheel may be indicated by the line 1). Theprojections onto the axial line of the wheel of the active grindingsurfaces of the serrations between these points may be indicated by theletter g. It Wlll be seen that the line 1) is longer than the combinedlengths of the lines g between the selected points.

Each of the machines illustrated in the drawings is provided withmechanism for shaping or truing the serrations of the grinding wheel.The truing mechanisms are similar in construction and, therefore, adescription of one is explanatory of both. The truing device isshown,more or less dia rammatically, in Fig. 2. A commercial em odimentis illustrated in Figs. 1, 12, 12", 13 and 14. Referring to thesefigures, and articularly to Fig. 12, 185 indicates a sli e mounted on asupport 186 for movement back and forth in parallelism with the axis ofthe grinding wheel. This support 186 may be located to that side of thegrinding wheel op osite the work holding means, as shown in ig. 1, or tothe same side, as shown in Figs. 4, 5 and 13. By preference, the truingdevice is pivotally supported in order that it may be thrown out of theway when not in use, To this end, it may be fixed to a.

shaft 17 2 journalled in suitable bearings 173. 66

In Fig. 1, these hearings 173 rise from the rear of the base 10. In themachine shown in Figs. 4 to 10, and Fig. 13, the bearm 173 are providedon a bracket 174 adjustab y fixed to the front face of the rocking bedI).

nped in position by a bolt 178 having on 7 its inner end (see F1 13) abushing 179 ada ted to engage a exible guard 180 carrie by the slide185. Mounted on the slide 185, for movement on lines which are parallelto the respective side faces of the serrations of the grindin wheel tobe trued, are slides 187 and 188 which carry, at their forward ends,diamond points 189 and 190, respectively. The slides 187 and 188 areguided by ways 191 (see Fi 14) fixed to the slide 185 by screws 192. orthe purpose of limiting the extent of movement of the slides and thediamond points carried thereby towards the wheel, each of the slides 187and 188 is provided with a set screw 193 adapted to engage the rear endof a respective way 191. The slides 187 and 188 may be longitudinallyreciprocated so as to move the respective diamond points back and forthacross the faces of the serrations, in any suitable manner, as, forinstance, by means of a lever 194 pivoted to the slide 185 as at 195 andhavin a bifurcated end 196 ada ted to straddle pins 197 carried by theslides 187 and 188. The truing means, comprising the diamond points, areindexed relatlvely to the grinding wheel so that they may successivelyoperate on the serrations and, to this end, the following arrangementmay be provided. 200 is a lead screw journalled in the support 186 andhavin threaded engagement with the slide 185. n the outer end of thisscrew is a handle 201 by means of which it may be rotated. Fixed to thescrew 200 is a pinion 202 meshing with a gear 203 fixed to the hub of adisk 204 journalled on a stud 205. This stud has a rectangular portion206 engaging in a horizontally extending slot 207 in a part of thesupport 186. The stud is clamped in adjusted position in the slot by a.nut 208. Fixed to the outer end of the stud and against rotation is anarm 209 provided wit-h a spring pressed plunger 210, the outer end ofwhich is provided with a handle or knob and the inner end of which isada ted to be engaged in a notch or slot 211 in t e disk 204.

When it is desired to true the serrations of the grinding wheel embodiedin the machine of Figs. 4 and 5, the truing device is thrown over to theoperative position shown in Figs. 4 and 13, and the inding wheel isadvanced into operative re ation b0 the Irving device as by turning thehand wheel 59. i gear 208 of such size will be by the pinie complete Ithe slide 185 d a distance corresponding to between adjacent serrationson the grin ing The support 186, together with the parts carried therebmay be adjusied axiaiiy of the grinding wheel, in order that the diamondpoints are in proper relation to the serrations, by turning the screw 116. After the truing device has been properly set up the slide 185 may bebrought to the position where the diamond point 190 will operate uponthe first convolution, and in this position the plunger 210 will engagein the notch 211 of the disk 204. The diamond point 199 will he movedback and forth by rocking; the free end of the handle s irst indexedposition so as to 1 face of the first serrao After the left he firstserration is thus 1" 210 is drawn out, and the ated by turning thehandle diamond point 190 is thus proper indexed relation to the theplunger 210 wili spring e V s or notch 20L thereby preventing furtherrotation of the screw 20%. The is now moved back and left hand face ofthe second the handle 194. he dis .ond point 196 is thus indexed tosucce i o positions moved back and forth across the corresponding sidefaces of jlie several serrations untii these side faces are properlytrued. Then the diamond selected this when it i forth "or e point 189wil be brough int) proper position to grind the right hand face of thefirst serration of the grinding wheei. The handle 194 will he reversedso that the bifurcated end 196 thereof straddles the pin 191' of theslide 18?. This handle will be rocked back and forth so that the diamondpoint will moved across the right hand face of the serration. Thediamond point 189 is successively indexed so as to operate upon theseveral serrations in the same manner as was the diamond point 190.After the wheel has been trued, the truing mechanism may be swung out ofthe way, and the grinding wheel may be moved into position to operate onthe work without changing the axial relation of the wheel and the workholder.

When the truing mechanism is employed for shaping or re-shaping thestepped serrated wheel of Fig. 1, the grinding wheel is moved rearwardlyto a position where the diamond points may operate upon the serrationsthereof. The diamond points are indexed axially of the grinding wheeland 4 we moved back and forth in each indexed position so as toresuriace the respective side faces of the serrations in the same mannor as the preceding embodiment, e2: cap: that the grinding wheel is meed rad aily as by turning the hand 2 very siight distance each tiirie e5mend points are indexed so that the serrations will be of increasingdiameter, w that they will be of snccessivel I widths at equal distancesfrom the wheei. The ositioning or may be determine by the scale or L ter22. More 'speciiicaliy; assuming" diamond points 189 and 196 here therespective faces of the first serratio the truing device wili he ind eright (Fig. l), and the grinding be moved slightly away from the t vice.The diamond points E39 and, 190 w ll then be moved back and forth facesof the second serrstion diamond points wiil then he again indexedthegrinding wheel will he move I a slight distance towards the fromachine, and the diamond points will then be moved back and forth totrue the faces of the third serration 25 This sequence of steps will berepeated until side faces of ail the serrations are properly trueoi. Allof the serrations will now be or" f shape and of progressivelyincreasing diameter. The side faces of the serrations are trued for aportion of their depths only because the grooves in the grinding wheelare substantiai y deeper than the extent to which the sorr tions projectinto the during the grinding operation The grinding wheel shown in betrued in the same manner as described in connection with the g rindirwheel shown in Fig. i and, additionsriy the edges of the serrations aretruncated so as to form flats. These flats, in the present illustrativedisclosure, are all of the same width and of progressively increasingdiame ters. To truncate the serrations or true the flats after theserrations have been truncated, one of the diamond points may beadjusted with respect to the serration 26 and then the slide 185 ismoved longitudinally so as to cause the diamond point to truncate thefirst serration 26. The grinding wheel is then moved slightly away fromthe diamond point and then the latter is moved axially of the wheel andacross the serration 26*, and this operation is repeated for thesuccessive serrations.

The truing device is shown more or less diagrammatically in Fig. 2. Theparts of this truin device which correspond to those just described bearcorresponding reference numerals, except that the same are primed. Themicrometer or scale-215 may be employed for properly indexing thediamond romenet the r true-d 216. The,

points. The slides 187' and 188' may be movsdbackandiorthby thescrewsdevice in this 1a 11- lustratsd sshavmg a central slide 17 carryadiamond gint or cutting tool 2 18.

tool may employed for roughing out the grooves in the w eel. It may alsobe employed to truncate the serrations. The serrat ons ma be made ofprogressively greatsdiameiers means:- as m receding em odimen i. e.,p081- ti the w eel at successive distances from truing device.

It'is of importance to note that, since the grooves in the grindingwheel are substantaally deeper than the extent to which the serrationsproject into the work during the operation, it is'jnecessary to true.side faces of the serrations for a portion 0 of their depths unify, andthus a more preciseand accurate rmof serrationcanbe more convenientobtained. In the preferred form of w eel, where the serrations are apartso as to grind non-adjacent convclntions of the thread-groove. there isimficient space between the convolutions to accommodate the diamondpoint, a feature which is of considerable importance, particularly incases where a thread of fine pitch is to be ground. Not only does thespacing of the serrations permit of a more ready accommodation for thediamond points and avoid the necessity of truing the roots of thegrooves, but it allows a closer scrutiny of the action of the diamondpoints upon the serrations during the truing process.

When it is desired to grind a thread of large lead an is such as shownin Fi the axis of the ding wheel is incdined dicularly the lead of thethread on the work. In this position, the serrations of the din wheelextend substantiall in the $3605 of the thread angle of ad work insteadof across the thread as would bethecaseifthe two axes were laced allel.In order to time anguldi'ly the wheel so that its serrations areinclined dingly to the lead of the thread, the journal boxes, whichcarry the grindin wheel spindles, maybe adjustably moun on arcuatebrackets. The mounting of the wheels in both embodiments is somewhatsimilar, and the general arrangement will be best understood from Fig.17. It will be zen-ceas s s an... a e m or no w engage the workftfheywill be of. such contour and size as to properly and respectivelyonthoseportmnsorfacesolths 0 mashasbeenplanned. Inthe resent serrationson the grinding wheel are trucd and shaped to desircdsize and-shape. Itis true that, with the arrangement shown in Figs. 15 16 and 17 one endserration will engage the work ightl above the point f on 7 t between te central serration and a work, while the other end serration will anthe work slighilly below the last mentions point and, for tical purposestrui the wheel, this deviation is negligibl an the grinding plans may beconsi e as substantially including the axis of the work and the point ofcontact between the work and the several serrations or, at least, a meanof those points of contact. The serrations on the grinding wheel may beof like size and shape, or they may he stepped to efiect incrementgrinding.

As many changes could be made in the above construction and manyapparently widely difierent embodiments of the invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description, or shown in the accompanyingdrawing, shall interpreted as il ustrative and not in a hmiting sense.

It is also to be understood that the lanage used in the following claimsis intended to cover all of the generic and specific features of theinvention herein described and all statements of the scope of theinvention which, as a matter of language, might be said to falltherebetwecn.

I claim as my invention:

1. In a machine for grinding on metal work pieces convolutionscorresponding in cross section to a screw thread and in combination,means for rotntably supporting a piece of work, a grinding wheel 0abrasive material havinga plurality of spaced concentric grindingserrations adapted to simultaneously operate upon a plurality ofconvolutions on the work and spaced apart a distance which isa-inultiple ofthe distance between adjacent convolutions on the work soas to allow for passing of a cooling fluid between the grinding wheeland the part of each convolution on the work during. the grindingoperation means for rotatably supporting the grinding wheel with itsserraranged to simultaneously g for rotateby supporting fry respondingin cross section to s screw thread, means for rotatablysupportmn thegrinning wheel with its serrations simuitnneonsly engagement with apluralitv oi convolutions on the work, means for moving the work inaccordance with the lead of the thread, means for rotating the work morethan one revolution while moving- :5 distance equal that betweencorresponding points of edjacent serrations, and means for supplying a.cooling fluid between the grinding when and each thread convolution.

3.1:; combination, a grinding abrasive material provided with ofparallel separated grindins of convolutionson a metal 1' 5 piece ofwofi, means for rotate ly supporting the grinding wheel in engagementwith the work, meens for moving the work lon itudinelly, the or tent ofsuch longitudina movement of the work through a, distance equai thatbetween corresponding points of adjacent serrations on the Wheel beinggreater than the projections onto the axis of the wheei of the activegrinding surfaces between said points, and means for supplying e coolingfinid be tween said grinding wheel and each convolution on the Work.

4. In a machine for simultaneously grindinga plurality of convointionson metal work pieces and in combination, means ior rotatab'ly supportinga, work piece, a. rotatable grlndin wheel of abrasive materiel havingspa serrations arranged to suecessively grind increments from enchconvolution formed in the work piece, and means for moving the work andwheel one relatively to the other generelly longitudi- .nally of thework to bringeach serretion into engagement with the successiveconvolutions on the work piece.

5. In combination, an abrasive grinding wheel having 5 seedcircumferential serrw tions correspon ing in cross section to a screwthread and varying in dimensions withrespect to one another so as togrind successive increments from successive convolutions of the work,means for supporting the work with the serrations of said whee! insimultaneous engagement with the convolutions on the work, and means formoving the work and wheel one relative to the other to 7 cause theserrations to successively operate upon each convolution on the work.

6. In combination, an abrasive um eren wheel having a plurality of tirethe other engagement the work piece and nee less grind ng serrationscorresponding in cross crew thread, means for rotatsbiy supportingsprees of work, means for rotetebly pportmgseid wheel with said eerretnnnitsneously engegin a plurality or nvolutions on the wor 1n thegrinding;

L and sngle and of pro ivel end chord-lengt' in sai 2-2;. rneens formoving the work genereliy longitudinally to bring the serrations intosnecessiveengegement with each convoluticn and ind increments therefrom.

In eomhinetion, a, grinding wheel hsv s plurality oi' sepsmte parallelsorretrons o; progressively memes size, means for roteteoiy supportingthe grinding wheel, means for supporting the work, rneens for moi-12gthe worir en wheel one relative to genereliy longitudinally of the workto cause theserrntions toprogressively grind successive increments fromeach con- VOiHiIIQ-E on the work, seid'serretions being specsd apart ata multi le ofthe distance between successive convoiiitions on the work,and means for passing ecooling fluid be tween the Wheei and eachconvolution on the work during the grinding operation.

8. The method of grinding screws, taps, and the like, which consists inbringing into a. grinding wheel nevin e plurality of separate sorretionsparallel to each other, movi the work piece and grinding wheellongitudineiiy one reintive to the other in accordance with the lead ofthe thread, rotating said grinding wheel, rotating said work more thanone revolution while relatively moving having spaced serrationssimultaneously efactive on a. plurality of convolutions on the wor andrelatively mov ng the work and whee to cause the successive serrationsto grind successive increments from the" convolutions.

10. The method of simultaneously inding a plurality of convolutions on aardened metal work piece by utilizing a. grinding wheel having a.plurality 0 separate,

parallel serrations of progressively inereesing width and diameter whichconsists in positioning the work and wheelso that the serrations extendinto the work progressively greater distances, rotating t e grindm wheeland work while in engagement, on

relatively moving the work an wheel lonn-iece, said serrations being ofthe

